Led assembly

ABSTRACT

This disclosure discloses an LED assembly. The LED assembly includes a transparent mount with a top surface and a bottom surface opposite to the top surface, an LED chip arranged on the top surface, an electrode plate, a first phosphor layer having a first phosphor, and a second phosphor layer having a second phosphor, wherein the transparent mount and the electrode plate substantially have a same width. The electrode plate is arranged on an edge of the top surface and electrically connected to the LED chip.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 15/297554, filed on Oct. 19, 2016, which is acontinuation application of U.S. patent application Ser. No. 14/493,940,filed on Sep. 23, 2014, which claims priority to and the benefit ofTaiwan Application Serial Number 102136176 filed on Oct. 7, 2013, whichis incorporated by reference in its entirety.

BACKGROUND

The present disclosure relates generally to light emitting diode (LED)assemblies and their applications, more specifically to the LEDassemblies suitable for omnidirectional light appliances.

LED has been used in different kinds of appliances in our life, such astraffic lights, car headlights, street lamps, computer indicators, flashlights, LCD backlight modules, and so on. LED chips, which are used aslight sources for appliances, are produced by wafer manufacturingprocess in the front end, and then undergo LED packaging in the back endto result in LED assemblies or apparatuses.

LED packaging mainly provides mechanical, electrical, thermal andoptical supports to LED chips. LED chips, which are kind ofsemiconductor products, are prone to degradation, or aging, if beingexposed for a long time in an atmosphere full of humidity or chemical.To isolate the LED chips from unfriendly atmosphere, epoxy resins arecommonly used to cover and seal them. Heat dissipation and lightextraction should be also considered for LED packaging, such that LEDproducts could have long lifespan and high brightness. For example, theheat generated at a p-n junction in an LED chip, if not being welldissipated, could deteriorate the LED chip, shorten its lifespan, anddowngrade its reliability. Optical design, such as the way to extractand direct the light into a desired angle or distribution, also plays animportant issue for LED packaging.

Design for packaging white LEDs is more complex and needs to furtherconsider color temperature, color rendering index, phosphor, etc. Awhite LED could be provided using phosphor to convert a portion of theblue light from a blue LED chip into green/yellow light, such that themixture of the lights is perceived as white light by human eyes. Becausehuman eyes are vulnerable to high-intensity blue light, the blue lightfrom a blue LED chip in a white LED package should not emit outwarddirectly without its intensity being attenuated. In other words, theblue light should be kind of “sealed” or “capsulated” so as to preventblue light leakage to human eyes.

Furthermore, it is a constant trend in the LED industry to pursue LEDpackaging processes with high stability, low cost, and high productyield.

SUMMARY

This disclosure discloses an LED assembly. The LED assembly includes asubstrate, a mount, a first LED chip, an electrode plate and a layer.The substrate has a first top surface. The mount has a second topsurface and a bottom surface which is opposite to the second top surfaceand is positioned on the first top surface in a configuration of forminga recess. The first LED chip includes a third top surface, and arrangedon the first top surface and in the recess. The electrode plate includesa fourth top surface, arranged on the second top surface, andelectrically connected to the first LED chip. The layer includes aphosphor, and covering the first LED chip, the first top surface, andthe electrode plate. The fourth top surface is higher than the third topsurface in an elevation from the first top surface.

This disclosure also discloses an LED blub. The LED bulb includes an LEDassembly, a holding element and a transparent cover. The LED assemblyincludes substrate, a mount, a first LED chip, an electrode plate and alayer. The substrate has a first top surface. The mount has a second topsurface and a bottom surface which is opposite to the second top surfaceand is positioned on the first top surface in a configuration of forminga recess. The first LED chip includes a third top surface, and arrangedon the first top surface and in the recess. The electrode plate includesa fourth top surface, arranged on the second top surface, andelectrically connected to the first LED chip. The layer includes aphosphor, and covering the first LED chip, the first top surface, andthe electrode plate. The fourth top surface is higher than the third topsurface in an elevation from the first top surface.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present disclosureare described with reference to the following drawings. In the drawings,like reference numerals refer to like parts throughout the variousfigures unless otherwise specified. These drawings are not necessarilydrawn to scale. Likewise, the relative sizes of elements illustrated bythe drawings may differ from the relative sizes depicted.

The disclosure can be more fully understood by the subsequent detaileddescription and examples with references made to the accompanyingdrawings, wherein:

FIG. 1 shows an LED assembly according to an embodiment of thedisclosure;

FIG. 2 shows a top view of the LED assembly in FIG. 1;

FIGS. 3A and 3B show two different cross sectional views of the LEDassembly in FIG. 1;

FIGS. 4A, 4B and 4C illustrate LED bulbs, each using the LED assembly ofFIG. 1 as its filament;

FIG. 5 demonstrates a method for manufacturing the LED assembly;

FIG. 6 shows the pattern on a transparent mount;

FIGS. 7A and 7B are cross sectional views of a transparent mount;

FIGS. 8A and 8B are cross sectional views of a transparent mount afterthe formation of a phosphor layer;

FIG. 9 demonstrates a transparent mount is attached on a transparentsubstrate using a phosphor layer as a glue layer;

FIGS. 10A and 10B are cross sectional views after a transparent mount issecured on a transparent substrate;

FIGS. 11A and 11B are cross sectional views after the formation ofconductive electrode plates;

FIGS. 12A and 12B are cross sectional views after mounting LED chips;

FIGS. 13A and 13B are cross sectional views after forming bonding wires;

FIGS. 14A and 14B are cross sectional views after the formation of aphosphor layer;

FIG. 15 demonstrates another method for manufacturing an LED assembly;

FIGS. 16A and 16B show two cross sectional views of the LED assemblyfabricated according to the method in FIG. 15; and

FIGS. 17A and 17B demonstrate two cross sectional views of another LEDassembly.

DETAILED DESCRIPTION

A perspective view of an LED assembly 100 according to an embodiment ofthe disclosure is described in detail with reference to FIG. 1, whileFIG. 2 shows a top view of the LED assembly 100. These drawings are onlyillustrative, and the dimensions or ratios therein are not intended tolimit the invention.

Shown in FIGS. 1 and 2, the LED assembly 100 has a laminate substrate105 with a rectangular top surface. The manufacturing method and thestructure of the laminate substrate 105 will be detailed later. On thetop surface of the laminate substrate 105, there are two conductiveelectrode plates 102 and 104 at two opposite ends respectively. Aphosphor layer 106 is formed on the top surface and positioned on anarea substantially between the two conductive electrode plates 102 and104.

FIGS. 3A and 3B show cross sectional views of the LED assembly 100,resulted from the cutting planes AA and BB respectively. As shown inFIGS. 3A and 3B, the laminate substrate 105 is composed of three layers,including a transparent substrate 112, a phosphor layer 114 and atransparent mount 116. The phosphor layer 114 is sandwiched between thetransparent mount 116 and the transparent substrate 112. Positioned onthe transparent mount 116 are the conductive electrode plates 102 and104, and LED chips 108. The phosphor layer 106 covers and surrounds theLED chips 108, which are mounted on the transparent mount 116, andtherefore the LED chips 108 are sandwiched between the phosphor layer106 and the transparent mount 116. Bonding wires 110 provide electricalinterconnection between the LED chips 108 and also electrically connecttwo of the LED chips 108 to the conductive electrode plates 102 and 104.

In this specification, “transparent” means having the property oftransmitting rays of visible light, and could refer to as transparent,translucent or semitransparent. In some embodiments, the transparentmount 116 and the transparent substrate 112 are not electricallyconductive, and could be made of the same or different material. Forexample, they could be sapphire, silicon carbide, or diamond-likecarbon.

The LED chips 108 in FIGS. 1, 2, 3A and 3B are all blue LED chips in oneembodiment and are mounted and arranged as a row on the transparentmount 116. This invention is not limited to the abovementioned,nevertheless. Based on desired applications, the LED chips 108 might bearranged to form any pattern on the transparent mount 116, which forinstance could have two or three rows. In other embodiments, some of theLED chips 108 emit blue light with a dominant wavelength ranging from430 nm to 480 nm, some emit red light with a dominant wavelength rangingfrom 630 nm to 670 nm, and some emit green light with a dominantwavelength ranging from 500 nm to 530 nm.

An LED chip 108 might have only one single LED cell, whose forwardvoltage is about 2 to 3 volts, and this kind of LED chip is referred toas a low-voltage LED chip hereinafter. Comparatively, an LED chip 108 inanother embodiment might include several LED cells connected in series,and is referred to as a high-voltage LED chip hereinafter, because itsforward voltage might be as high as 12V, 24V, or 48V, much higher thanthat of a low-voltage LED chip. In one high-voltage LED chip, each LEDcell has a light-emitting layer, and the LED cell might be formed on anepitaxial or non-epitaxial substrate. More specifically, the LED cellsin the high-voltage LED chip are electrically connected to each other ona common substrate; not by wire bonding but by some patterned conductivestrips produced by wafer processes, such as metallization or lithographythat processes all the LED cells at the same time. The common substratemight be an epitaxial or non-epitaxial substrate. In FIGS. 1, 2, 3A and3B, the LED chips 108 are connected in series so the forward voltage isthe summation of the forward voltages of the individual LED chips 108.This disclosure is not limited to the abovementioned, however. In someembodiments, the LED chips 108 could be connected in many differentconfigurations, including series, parallel, bridge or any combinationthereof.

Trenches 109 a, 109 b, 109 c and 109 d are formed in the transparentmount 116. Trenches 109 a and 109 b shown in FIG. 3A are substantiallyin parallel to each other, and trenches 109 c and 109 d shown in FIG. 3Bare substantially in parallel to each other. As derivable from FIGS. 3Aand 3B, the trenches 109 a, 109 b, 109 c and 109 d are positioned tosubstantially surround the LED chips 108. In other words, the area wherethe LED chips 108 is mounted on the transparent mount 116 is between thetrenches 109 a and 109 b, and between trenches 109 c and 109 d as well.As shown in FIGS. 3A and 3B, the phosphor layer 106 entirely fills upthe trenches 109 a, 109 b, 109 c and 109 d, and through them contactsthe phosphor layer 114.

Both the phosphor layers 106 and 114 have at least one kind of phosphor.For example, the phosphor in the phosphor layers 106 and 114 could beexcited by the blue light (with a dominant wavelength of 430 nm˜480 nm)emitted from the LED chips 108 to generate yellow light (with a dominantwavelength of 570 nm˜590 nm) or yellowish-green light (with a dominantwavelength of 540 nm˜570 nm), such that the mixture is perceivable aswhite light by human eyes. The phosphor layers 106 and 114 could betransparent body in which phosphor is dispersed. The transparent body isepoxy resin, or silicone for example. The phosphor in the phosphor layer106 might be the same as or different from that in the phosphor layer114. The phosphor could include, but is not limited to, yttrium aluminumgarnet (YAG), or terbium aluminum garnet (TAG). The phosphor layers 106and 114 might have one or more kinds of phosphor. For instance, in oneembodiment the phosphor layers 106 and 114 have two kinds of phosphor,one emitting yellow light and the other emitting red light. Phosphoremitting green light could be also included in some embodiments.

A phosphor capsule formed by the phosphor layers 106 and 114substantially encapsulates each LED chip 108. The light emitted from theLED chips 108, whether it goes upward or sideward, confronts thephosphor layer 106 and the light emitted from the LED chips 108, whetherit goes downward, confronts the phosphor layer 114. In case that some ofthe LED chips 108 are blue LED chips, the blue light therefrom excitesthe phosphor in the phosphor layer 106 or 114 to generate a yellow lightor yellowish-green light such that a mixing light of the blue light andthe yellow light or yellowish-green light is sensed by a human eye as awhite light, so that the total intensity of the blue light is attenuatedto avoid any harmful effect to human eyes.

FIG. 4A illustrates an LED bulb 200 a using the LED assembly 100 as itsfilament. The LED bulb 200 a has two clamps 202, each of which might bein a shape of V or Y. The clamps 202 are made of conductive material,and the two projecting prongs of each clamp 202 clamp one conductiveelectrode plate (either 102 or 104) to hold the LED assembly 100 withina cover 204 of the LED bulb 200 a. In FIG. 4A, the surface with thephosphor layer 106 faces upward (along the z direction). The clamps 202also electrically connect both the conductive electrode plates 102 and104 to the Edison screw base 203 of the LED bulb 200 a, which providesthe electric power required for the LED assembly 100 to emit light. FIG.4B is similar with FIG. 4A, but differs in the direction that the LEDassembly 100 faces. In FIG. 4B, the surface of the LED assembly 100having the phosphor layer 106 faces sideward (along the y direction),and is substantially perpendicular with the screw axis (along the zdirection) of the LED bulb 200 b in FIG. 4B. FIG. 4C is similar withFIG. 4B, but differs in that the supports 209 are solid strips with arectangular shape. Each of the supports 209 has a notch 213 at its endto support the LED assembly 100 within a cover 204 of the LED bulb 200c. The supports 209 could be made of metal or some kind of conductivematerial, capable of conducting electric current from the Edison screwbase 203 to the conductive electrode plates 102 and 104 at ends of theLED assembly 100. Because of the transparency of the transparentsubstrate 112 and the transparent mount 116, the LED bulb 200 a, 200 band 200 c all could be omnidirectional lighting apparatuses.

FIG. 5 demonstrates a process flow for manufacturing the LED assembly100. The steps are detailed in reference with the following drawings.

Regarding to step 302, a sheet of the transparent mount 116 is providedand has a plurality of the same or similar repeated patterns on itssurface as shown in FIG. 6. The pattern on the transparent mount 116 inFIG. 6 has 2 rows in a horizontal direction and 4 columns in a verticaldirection to produce eight LED assemblies 100 at one time. The examplein FIG. 6 is not intended to limit the invention. From one single sheet,some embodiments of the invention could produce only one LED assembly100, and others might produce more than 8 LED assemblies 100.

The pattern in FIG. 6 is composed of trenches 109 a, 109 b, 109 c, 109d, 109 e, and 109 f, where the trenches 109 a are substantially inparallel to the trenches 109 b, and the trenches 109 c are substantiallyin parallel to the trenches 109 d. FIGS. 7A and 7B are cross sectionalviews of the transparent mount 116 resulted from the cutting planes AAand BB in FIG. 6 respectively. The trenches 109 a, 109 b, 109 c and 109d substantially enclose the area where the LED chips 108 are going to bemounted. The trenches 109 e and 109 f substantially define the locationfor a single LED assembly 100, to ease the singulation in the followingstep which will be detailed later. The trenches 109 a, 109 b, 109 c, 109d, 109 e, and 109 f might be formed by dry or wet etching, for example.

Regarding to step 304, coating or spraying is used to form the phosphorlayer 114 on the transparent substrate 112, as demonstrated in FIGS. 8Aand 8B. Some ditches are formed in the transparent substrate 112 priorto the formation of the phosphor layer 114. These ditches preferablylocate just under the trenches 109 e and 109 f after the transparentmount 116 stacks on the transparent substrate 112 for easilysingulating.

Regarding to step 306, the transparent mount 116 is attached on thetransparent substrate 112 using the phosphor layer 114 or an additionaltransparent material as a glue layer, as demonstrated in FIG. 9. FIGS.10A and 10B are cross sectional views corresponding to FIGS. 7A and 7Bafter the transparent mount 116 is attached on the transparent substrate112.

Regarding to step 308, the conductive electrode plates 102 and 104 areformed on the transparent mount 116, as demonstrated in FIGS. 11A and11B. Some metal films or strips could be attached on proper areas of thetransparent mount 116 to be the conductive electrode plates 102 and 104.

Referring to Step 310, the LED chips 108 are mounted on the transparentmount 116 by way of silver paste for example, as shown in FIGS. 12A and12B which respectively correspond to FIGS. 11A and 11B.

Referring to Step 312, bonding wires 110 are formed to provide electricinterconnection between the LED chips 108, and between the LED chips 108and the conductive electrode plates 102 and 104, as demonstrated inFIGS. 13A and 13B, which respectively correspond to FIGS. 12A and 12B.

Regarding to step 314, the phosphor layer 106 is formed to cover or sealthe bonding wires 110, the LED chips 108, and the trenches 109 a, 109 b,109 c and 109 d, as shown in FIGS. 14A and 14B, which respectivelycorrespond to FIGS. 13A and 13B. In FIGS. 14A and 14B, the phosphorlayer 106 does not extend over the trenches 109 e and 109 f. In oneembodiment, the phosphor layer 106 is formed on the LED chips 108 bydispensing.

Referring to Step 316, the transparent substrate 112 and the transparentmount 116 are singulated, by cleaving, laser cutting, carbon dioxidelaser cutting, for example to form a plurality of individual LEDassemblies 100. As aforementioned, the transparent mount 116 is capableof produce eight LED assemblies 100 at one time. These LED assemblies100 in FIGS. 14A and 14B could be separated by cleaving along thetrenches 109 e and 109 f, so as to finalize the LED assemblies 100,whose cross sectional views have been demonstrated in FIGS. 3A and 3B,which respectively correspond to FIGS. 14A and 14B.

The method exemplified in FIG. 5 produces no pattern at the backside ofthe transparent substrate 112. Therefore, handling, holding orsupporting the transparent substrate 112 could be done via the backsideof the transparent substrate 112 where scratches are not a concern.Accordingly, the yield rate of the LED assemblies 100 could be improved.

In another embodiment, some of the phosphor layer 106 is inside thetrenches 109 a, 109 b, 109 c, and 109 c, but does not completely fillthem up. The phosphor 106, nevertheless, preferably covers at least onesidewall in each of the trenches 109 a, 109 b, 109 c, and 109 c suchthat the phosphor 106 form walls inside the trenches to surround thearea where the LED chips 108 are disposed.

The bonding wires 110 are used for electrical interconnection in FIGS.3A and 3B, but this invention is not limited to this embodiment. Anotherembodiment of this disclosure has a printed circuit on the transparentsubstrate 116, and the LED chips 108 are flipped over to mount on theprinted circuit, which provides the interconnection between the LEDchips 108. As to the electrical connection to the conductive electrodeplates 102 and 104, it could be done using the bonding wires 110 or aprinted circuit as well.

FIG. 15 demonstrates another method for manufacturing an LED assembly,and FIGS. 16A and 16B are cross sectional views of the LED assembly 600produced according to the method illustrated in FIG. 15. The similaritybetween FIGS. 15 and 5 is comprehensible according to the disclosedteaching and will be omitted herein for brevity. Different from FIG. 5,in FIG. 15, an additional step 307 is inserted between steps 306 and308, and another step 314 a is in exchange for step 314.

In Step 307, a phosphor layer 107 fills in the trench 109 a, 109 b, 109c and 109 d, as demonstrated in FIGS. 16A and 16B. In one embodiment,the top surface of the phosphor layer 107 is even with that of thetransparent mount 116, or in other words the two top surfaces arecoplanar. The phosphor layer 107 formed by step 307 could avoid theoccurrence of the side leakage of blue light. After the formation of thephosphor layer 107, in step 314 a, the phosphor layer 106 is formed tocover the LED chips 108 and the bonding wires 110. The phosphor layer106 in FIG. 16A does not extend over the phosphor layer 107 or thetrenches 109 a and 109 b. Nevertheless, in step 314 a, a phosphor layer106 can be formed to cover the phosphor layer 107 or the trenches 109 aand 109 b in some other embodiments. Demonstrated in FIG. 16B, thephosphor layer 106 covers or extends over the trenches 109 c and 109 d.In the embodiment exemplified in FIGS. 16A and 16B, the LED chips 108are substantially enclosed by a phosphor capsule composed of thephosphor layers 106, 114, and 107. The light emitted from the LED chips108 will encounter the phosphor layer 106 and 107 if going upward andsideward, or the phosphor layer 114 if going downward. Therefore, theLED assembly 600 could avoid blue light leakage. The phosphors in thephosphor layers 106, 107, and 114 could be the same, similar ordifferent.

In FIGS. 3A, 3B, 16A, and 16B, the trenches 109 a, 109 b, 109 c, and 109d penetrate through the transparent mount 116, so that the phosphorlayer 106 or 107 can contact with the phosphor layer 114 via thesetrenches. This invention is not limited to the abovementioned, however.FIGS. 17A and 17B demonstrate two cross sectional views of another LEDassembly 700, and their similarity with FIGS. 3A and 3B are omittedherein for brevity. The trenches 109 a, 109 b, 109 c and 109 d in FIGS.17A and 17B do not penetrate the transparent mount 116, which means thetrenches 109 a, 109 b, 109 c and 109 d are shallower in comparison withthose in FIGS. 3A and 3B, and each has a bottom larger than 0 μm but notmore than 150 μm apart from the top surface of the phosphor layer 114.The phosphor layer 106 does not contact with the phosphor layer 114. Thelight from the LED chips 108 could not leak through the gap between thephosphor layers 106 and 114 if the gap is less than 150 μm.

In FIGS. 17A and 17B, the LED chips 108 are mounted on a bottom ofamounting trench 109 g between the trenches 109 c, 109 d and can avoidblue light leakage.

Some LED assemblies of the disclosure could be used as a filament in anLED bulb to form an omnidirectional lighting apparatus. Some LEDassemblies of the disclosure has a blank backside with no pattern, whichis immune from scratches and convenient for being contacted, held, orvacuumed during manufacturing processes.

While the disclosure has been described by way of example and in termsof preferred embodiment, it is to be understood that the disclosure isnot limited thereto. To the contrary, it is intended to cover variousmodifications and similar arrangements (as would be apparent to thoseskilled in the art). Therefore, the scope of the appended claims shouldbe accorded the broadest interpretation so as to encompass all suchmodifications and similar arrangements.

What is claimed is:
 1. An LED assembly, comprising: a substratecomprising a first top surface; a mount, comprising a second top surfaceand a bottom surface which is opposite to the second top surface and ispositioned on the first top surface in a configuration of forming arecess; a first LED chip, comprising a third top surface, and arrangedon the first top surface and in the recess; an electrode plate,comprising a fourth top surface, arranged on the second top surface, andelectrically connected to the first LED chip; and a layer, comprising aphosphor, and covering the first LED chip, the first top surface, andthe electrode plate, wherein the fourth top surface is higher than thethird top surface in an elevation from the first top surface.
 2. The LEDassembly of claim 1, further comprising a glue layer arranged betweenthe substrate and the mount.
 3. The LED assembly of claim 2, wherein theglue layer directly contacts the substrate and the mount.
 4. The LEDassembly of claim 1, wherein the layer has a curved surface.
 5. The LEDassembly of claim 1, wherein the layer directly contact a portion of thesecond top surface.
 6. The LED assembly of claim 1, further comprising afirst bonding wire electrically connected to the first LED chip and theelectrode plate.
 7. The LED assembly of claim 1, further comprising asecond LED chip formed in the recess.
 8. The LED assembly of claim 7,further comprising a second bonding wire electrically connected to thefirst LED chip and the second LED chip.
 9. The LED assembly of claim 8,wherein the layer covers the second bonding wire.
 10. The LED assemblyof claim 7, wherein the layer covers the second LED chip.
 11. The LEDassembly of claim 7, wherein the layer is filled between the first LEDchip and the second LED chip.
 12. The LED assembly of claim 1, whereinthe first LED chip comprises a plurality of LED cells formed on a commonsubstrate.
 13. An LED bulb, comprising: an LED assembly comprising: asubstrate comprising a first top surface; a mount, comprising a secondtop surface and a bottom surface which is opposite to the second topsurface and is positioned on the first top surface in a configuration ofa recess; a first LED chip, comprising a third top surface, and arrangedon the first top surface and in the recess; an electrode plate,comprising a fourth top surface, arranged on the second top surface, andelectrically connected to the first LED chip; and a layer, comprising aphosphor, and covering the first LED chip, the first top surface, andthe electrode plate; a holding element physically connected to the firstelectrode plate; and a transparent cover covering the LED assembly,wherein the fourth top surface is higher than the third top surface inan elevation from the first top surface.
 14. The LED bulb of claim 13,wherein the holding element comprises a clamp configured to fasten theLED assembly.
 15. The LED bulb of claim 13, wherein the holding elementcomprises a solid strip.
 16. The LED bulb of claim 15, wherein the solidstrip comprises a notch.
 17. The LED bulb of claim 13, wherein theholding element is electrically connected to the electrode plate. 18.The LED bulb of claim 13, wherein the LED bulb is configured to producean omnidirectional light.